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Derivatives (Notional Volumes of Outstanding HFT Derivatives) (Details) MWh in Millions, MMBTU in Millions, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) MMBTU MWh
Foreign Exchange Option [Member] | 2019 [Member} |
Derivative [Line Items] |
Derivative, Notional Amount | $ | $ 0
Foreign Exchange Option [Member] | 2020 [Member] |
Derivative [Line Items] |
Derivative, Notional Amount | $ | 0
Foreign Exchange Option [Member] | 2021 [Member] |
Derivative [Line Items] |
Derivative, Notional Amount | $ | 0
Foreign Exchange Option [Member] | 2022 [Member] |
Derivative [Line Items] |
Derivative, Notional Amount | $ | 0
Foreign Exchange Option [Member] | 2023 [Member] |
Derivative [Line Items] |
Derivative, Notional Amount | $ | $ 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Sales [Member] | 2019 [Member} |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 247
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Sales [Member] | 2020 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 42
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Sales [Member] | 2021 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 9
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Sales [Member] | 2022 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 2
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Sales [Member] | 2023 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Cost of Sales [Member] | 2019 [Member} |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 308
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Cost of Sales [Member] | 2020 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 108
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Cost of Sales [Member] | 2021 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 71
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Cost of Sales [Member] | 2022 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 50
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Natural Gas [Member] | Cost of Sales [Member] | 2023 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 41
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Sales [Member] | 2019 [Member} |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 5
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Sales [Member] | 2020 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Sales [Member] | 2021 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Sales [Member] | 2022 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Sales [Member] | 2023 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Cost of Sales [Member] | 2019 [Member} |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 6
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Cost of Sales [Member] | 2020 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Cost of Sales [Member] | 2021 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Cost of Sales [Member] | 2022 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0
Designated as Hedging Instrument [Member] | Held for Trading Hedge [Member] | Power [Member] | Cost of Sales [Member] | 2023 [Member] |
Derivative [Line Items] |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 0

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